Tearing tester



A. ELMENDORF.

TEARING TESTER.

APPLICATION FILED AUG.3I, 1920.

Patented July 25, 1922.

ABMIN ELMENDORF, OF CHICAGO, ILLINOIS.

TEARING TESTER.

This invention relates to a device for the purpose of testing thetearing strength of paper, fabrics, rubber, leather, cords, and othermaterials.

An object of my'invention is the construction of a device to measure thetea-ring strength of -materials by determining the work necessary toaccomplish the tearing. My device, instead of measuring the tearingforce directly, which method has been found to be unreliable because ofthe non-uniform 'structure of the materials acted upon,

measures the work-donein tearing the material.

A further object of my invention is to utilize a calibrated pendulumhaving thereon means to grip a specimen of the material to be tested.

A further object of my invention is the production of a deviceconsisting of a few simple parts, which results in a machine which doesnot easily get out of order and is readily repaired if any of the partsbecome worn or broken.

With my invention I use a certain sized specimen of the material to betested. This enables me to make calculations by which the strength ofthe material can be accurately determined.

' This application is a continuation of an application filed February 3,1920, Serial No. 356,078.

In order to accomplish these and other objects, I have embodied myinvention in a form of the device which is illustrated in theaccompanying drawings, in which:

Figure 1 is a front elevation of my device;

Figure 2 is a side elevation thereof;

Figure 3 is a plan view of the material to be tested shown cut but notfolded;

Figure 4 is an edge view of the material Specification of LettersPatent.

Patented July 25, 1922.

356,078, filed. February 3. 1920. This application filed August 31,

1920. Serial No. 407,165.

with the cut parts folded at right angles to the uncut parts, and

Figure 5 is a half section through the hub of the pendulum.

Referring to the drawings, a frame 1 has a base 2 which is supported onlegs 3. One of said legs has screw means 4 to enable the device to beplaced in a horizontal position. An axle 5 in the upper part of theframe has mounted thereon a hub 6. to which is attached by means ofbolts or rivets 6 a pendulum 6 The hub and pendulum may, of course, beintegral. This pendulum may be mounted on the shaft by roller bearings 7The pendulum 6 may be of any desired form, but as shown it consists ofa. thin plate having the general outline of a sector which isapproximately five-twelfths the area of a circle. The are of this sectoris calibrated from zero to seventy degrees each way.

Mounted frictionally on the hub of the pendulum is a pointer 8, havingat the upper end thereof a balancing knob 9, and at the lower endthereof a right-angled extension 10 by means of which the pointer may beset so that the scratch ll registers with zero on the pendulum. It willbe understood that zero is placed on the circumference of the pendulumso that a vertical line will pass through zero and the center of theaxle. This registration is accomplished by means of a screw 12 extendingthrough a standard 13 on the base 2 and coming in contact with theright-angled extension 10 on the end of the pointer 8.

Attached to a. triangular extension 14 on the edge of the pendulum is aspring clamp 15 which cooperates with a second spring clamp to hold thespecimen to be tested. An arm 16 of this clamp is attached to' thependulum by means of rivets 17, or in any other suitable way. A handle18 is used to open the clamp in order to insert the specimen ofmaterial;

is cut as indicated M34. The part 35 is a-t Attached to the arm. 19 ofthe I frame 1 is a second spring clamp 20. This tached tothe clamp onthe pendulum, while the parts 36 are attached to the clamp on the upperarm of the frame. The specimens may be of any desired suitable, definitesize. I have shown in this application and have made my calculationsbased on a specimen which is two inches in width measuring from the endsof the cuts.

A spring 23, one end of which is attached to the base, has the free endthereof pressed against the circumference of the pendulum. The force ofthis spring is such that it will hold the pendulum or retard theswinging so as to bring it to a stop after the specimen has been tornand the pendulum is beginning the return swing. In addition to dampeningthe vibrations after the specimen has been torn, the spring holds thependulum in the farthest position while the specimen is being gripped.

The operation of my device may be described as follows: The pendulumwhich was atrest and registers zero when hanging freely, is swung to theleft until the edge passes the end of the spring 23 which then springsup and engages the end of the radial edge of the pendulum. The specimenis then inserted so that the lips are held by the respective clamps.This done the machine is ready to make the tear. The spring 23 ispressed down with a finger and held so as to clear the circular edge ofthe pendulum until the specimen has been torn and the pendulum has begunthe return swing when it is allowed to spring up to dampen thevibrations, and stop the swinging. The machine is so designed that theline through the center of gravity of the pendulum and the axis ofrotation rotates through an angle of degrees when the pendulum is swungto the left to its starting position. This angle will be spoken of asthe initial angle. Other initial angles both greater and less than 70degrees may be used with equal satisfaction. It is only necessary toincrease the size of the pendulum to effect such a change. As thependulum is completing the tearing swing the pointer 8 is pushed aroundby the stop screw 12 until the end of the swing when it recedes with thependulum and records the maximum. angle the pendulum made to the rightof the vertical. The slight friction at the hub where it is attachedholds the pointer in a fixed position relative to the pendulum untilsuch a time as the operator reads the angle. This angle will be referredto as the final angle.

In computing the work done in tearing the specimen I will denote theinitial angleby 6 and the final angle by e,,. If W represents the weightofthe pendulum and cl the distance from the axis of rotation to thecenter of gravity of the pendulum then the work done in tearing is givenby the expression \Vd (cos e -cos e Dividing by the length of the tear,which is 2 inches in the machine illustrated, gives the average tearingforce.

The arm of the pendulum is readily calibrated so that the averagetearing force is read directly, thereby eliminating the computationsdescribed.

I claim: I

1. In a testing device, a frame, a pendulum mounted to rotate thereon,said pendulum being calibrated, a clamp attached to said pendulum, asecond clamp attached to said frame and adapted to cooperate wit-h saidfirst clamp to hold material to be tested, and a pointer frictionallymounted. on the hub of said pendulum and cooperating with said pendulumto measure the work done in tearing the material.

2. In a testing device, a frame, lum mounted to rotate thereon, saidpendulum being calibrated, a clamp attached to said pendulum, a secondclamp attached to said frame and adapted to cooperate with said firstclamp to hold material to be tested, and a balanced pointer frictionallymounted on the hub of said pendulum and cooperating with said pendulumto measure the work done in tearing the material.

3. In a testing device, a frame, lum mounted to rotate thereon, saidpendulum being calibrated, a clamp attached to said pendulum, a secondclamp attached to said frame and adapted to cooperate with said firstclamp to hold material to be tested, means cooperating with saidpendulum to measure the work done in tearing the material, and means tohold said pendulum in position to attach the specimento be tested and torelease said pendulum from its held 105 position.

4. In a testing device, a frame, a pendulum mounted to rotate thereon,said pendulum being calibrated, a clamp attached to said pendulum, asecond clamp attached to 110 said frame and adapted to cooperate withsaid first clamp to hold material to be tested, means cooperatingwithsaid pendulum to measure the work done in tearing the material, andspring means to hold said pen- 115 dulum in position to attach thespecimen to be tested and to release said pendulum from its heldposition. I

5. In a bearing tester, a frame, a pendulum mounted to rotate thereon,said pendulum being calibrated, a clamp attached to said pendulum, asecond clamp attached to said frame and adapted to cooperate with saidfirst clamp to hold the material to be tested, and means cooperating.with said 12 pendulum to measure the work done in tearing the material,and means to hold said pendulum in position to attach the specimen to hetested, to release said pendulum from its held position, whereby itswings to tear said 30 a pendumaterial, and to bring said pendulum to astop after it has swung.

6. In a testing device, a frame, a pendulum mounted to rotate thereon,said pendu- 5 lum bein calibrated, a clamp attached to said pen ulum, asecond clamp attached to said frame and adapted to cooperate with saidfirst clamp to hold material to be tested,

a pointer frictionally mounted on the hub of said pendulum andcooperating with said 10 pendulum to measure the work done in tearingthe material, and means to set said pointer at zero on said pendulum.

In testimony whereof I 'aflix my signature.

A-RMIN ELMENDORF.

